Three days ago I scan the ECM on my 2002 Nissan Altima with OBD II scanner and came back with Nissan Anti Theft System Malfunction.

Because we tried to start the car more than five times that the computer has it in lockdown mode.

Does anyone know if the Anti Theft system can be disabled? I live in an area where auto theft is non-existent. What's happening now is that the computer is not even recognizing my transponder key. The only solution now is to tow the car to the dealer and clear the ECM.

If the anti theft system can be disabled without affecting the ECM or BCM I would rather go this route.

Or if anyone know how to clear the trouble code in the ECM without any tool would be appreciated. Thanks.

Last week Wednesday I finally towed my car to the dealer. I wrote down everything that I did on the car that is crankshaft and camshaft sensors changed, OBD II scan the ECM and what the DTC's were etc., and gave to service advisor so Tech knows what's happening.

On Friday they called me and asked for the Master ignition key. For about two years now, I've been using the spare or valet key as I had lost the master key. They said they needed the master as it is programmed differently than the spare key. Master key has more capabilities.

I asked service advisor if valet key can be reprogrammed like master key. He said the chip in each key is different. My brain cannot reconcile why the two keys have different chips. My brain was saying, it has the same chip but valet key has less stuff in it but it can be expanded to become a master key. Service advisor said logic dictates it should be but its not.

I agreed to have a master key made but then they are out of stock and have to order it.

I wonder if anyone has any experience with regard to the differences between the two keys. Thanks a lot.

As far as I know the chips inside the keys are the same but with the different frequency. Thew difference between the master key and the spare (valet) key is that the valet key can't open the glove box, trunk or rear seats lock.

From the owners manual:

Quote:

NISSAN VEHICLE IMMOBILIZER SYSTEM (NVIS) KEYS

You can only drive your vehicle using the master or valet keys which are registered to
the Nissan Vehicle Immobilizer System components in your vehicle. These keys have a transponder chip in the key head.

The master key can be used for all the locks.

The valet key cannot be used for the trunk lid glove box lock or rear seatback lock.

To protect belongings when you leave a key with someone, give them the valet key only.

Thanks Tech. That's exactly what I read about the difference between the master and valet key.

I was going to have a new key made anyway and the cost is the same with a locksmith. Probably its the same locksmith the dealer calls to cut the key. Service advisor also pull up a couple recall items for my car. I remember the ECM recall I did not bring the car in cause it wasn't giving me any trouble.

eltiar - If you can get hold of an OBD II scanner that will be great. Scan your ECM for trouble codes. DTCs P1610 - P1615 refers to NATS malfunction. Also, if your security light ( on the dashboard) comes on while cranking your car definitely has something to do with your anti theft system.

Nissan Tech said only dealer can clear this so you gonna have to bring your car to the dealer. Also disconnect the battery for at least 4 hours, reconnect and try start again. But I think once the computer put the car in lockdown mode, it needs to be cleared in the ECM and BCM before it starts.

Hi,
My valet key would not start my 02 Altima and I wanted an extra "master" key so I went to the dealer, they took all my keys and programmed them, now my valet key works... In and out 45 minutes. HTH

Service advisor called me today and told me car wants to start but then it cuts off. The problem is definitely in the Anti Theft System. He said its the Amp located in the or attached to the ignition cylinder either shorted or open and not sending a signal to the ECM. The dealer's is about $224. plus labor so roughly a $380. job. So I'm tyring to locate one in the internet.

Cany anyone tell me what this part is, what exactly does it do and how hard is it to replace. Thanks a lot.

This is a follow-up on my previous thread. I talked to a parts person from a different Nissan dealer. I mentioned about the Amp that service advisor said from another Nissan dealer.

He said the service advisor may be referring to the Anti Theft Immobilizer Control Unit. Service advisor said it may be shorted and needs to be replaced. Service advisor said it needs to be reprogrammed after new part is installed.

rightsaidfred - scan the ECM for trouble codes would be the best start. This way you take the guesswork out of the process.

If your problem is with the NATS then it cuts out the fuel to prevent from starting. My problem is the malfunction of the Control Unit - Immobilizer. It's not receiving signal from the key and transmit to the ECM. I ordered it online and I save me $100. Nissan dealer service advisor allowed me to order the part myself. I pay them the labor for installation and reprogramming.

Installation is actually easy. You still have to take the car to dealer for reprogramming the new part. In my case I already towed the car to dealer. I'm not going to take it out of the dealer shop, install the immobilizer and tow it back to dealer. Just to much hassle. Good luck.

Well, I finally got my car back from the dealer shop last Friday. My initial problem of no start was a failed Control Unit Immobilizer. This receives signal from the transponder key and sends it to the ECM. Car is now up and running.

But, dealer did a recall work and replaced the crankshaft and camshaft sensors with the old design plastic parts. A month ago I had already replaced the both with the new redesigned parts which is metal and cylindrical shape.

Car now runs rough. When I got home I re-installed the new crankshaft and camshaft parts. The SES light is also on now.

If I let dealer do a new diagnostic work on the SES I have to pay again. They told me the previous job was for the no start only. If anyone has experience on this I would appreciate it very much your feedback.

P. S.- It is now clear to me that an OBD II scanner is now a necessary tool to have like a screwdriver. I am now looking for one that supports all five protocols.

Put the plastic ones back in...If it still runs rough then take it back. My 02 has had no problems with the oem style. Just make sure there are no other issues. ie there is no cyl. comp. issue, bad sp. plug or boot etc etc bla bla bla

Thanks missiletom. I actually switched back and forth between the metal and plastic camshaft sensor. Car still misfire and no power.

I have found a freelance mechanic who will scan the ECM for $25. The dealer charges $110. to diagnose the misfire because its a different issue from the original issue of no start.

I live in an island where we get only one of just about everything, lol. One Nissan, Chevy, Ford, etc, etc. dealer. Service advisor allowed me to purchase the Nissan part outside and I got one online where I saved $90 for the Control Unit Immobilizer.

Like you said, I make sure there aren't other issues like bad plugs, etc. and I'll find out after the scan. Thanks.